The invention relates to a process for carrying out catalytic conversions in which a catalyst is used consisting at least partly of a crystalline silica.
In U.S. Pat. No. 4,061,724 granted to Union Carbide Corporation a novel crystalline silica is described. The crystalline silica, denominated silicalite, is characterized in having the following properties after calcining in air for 1 hour at 600.degree. C.:
(1) Specific density at 25.degree. C.: 1.70.+-.0.05 g/ml; PA0 (2) Average refractive index: 1.39.+-.0.01; PA0 (3) An X-ray powder diffraction pattern in which the six lines in Table A are the strongest lines. PA0 (4) Crystals with an orthorhombic structure having the following unit cell parameters: EQU a=20.05 A, b=20.0 A and c=13.4 A PA0 (accuracy of each of these values .+-.0.1 A) PA0 (5) Pore diameter: about 6 A; PA0 (6) Pore volume: 0.18 ml/g. PA0 150-700 moles H.sub.2 O, PA0 13-50 moles SiO.sub.2, PA0 0-6.5 moles Me.sub.2 O. PA0 (1) Catalytic cracking of heavy hydrocarbon oils for the preparation of light hydrocarbon oil distillates; PA0 (2) preparation of isoparaffins by isomerization of n-paraffins; PA0 (3) hydrodesulphurization of hydrocarbon oil distillates; PA0 (4) conversion of naphthenes into aromatics; PA0 (5) polymerization of olefins for the preparation of polyolefins; PA0 (6) hydrocracking of heavy hydrocarbon oils for the preparation of light hydrocarbon oil distillates, such as the conversion of gas oil into gasoline; PA0 (7) hydrocracking of heavy hydrocarbon oils for the preparation of lubricating oils with a high viscosity index; PA0 (8) improving the light and oxidation stability of lubricating oils; PA0 (9) improving the octane number of gasoline; PA0 (10) preparation of olefins from lower alcohols and/or ethers; PA0 (11) preparation of olefinic gasoline with a low aromatics content from lower olefins or mixtures thereof with lower paraffins; PA0 (12) hydrodewaxing of hydrocarbon oils such as lubricating oil and fuel for jet engines; PA0 (13) transalkylation of alkyl-substituted aromatics, such as the preparation of ethylebenzene from a mixture of benzene and diethylbenzene; PA0 (14) alkylation of aromatics such as the preparation of ethylbenzene from benzene and ethylene. PA0 (1) Catalytic dewaxing of gas oil for improving the cloud point; PA0 (2) preparation of p-xylene by isomerization of other C.sub.8 aromatics; PA0 (3) preparation of p-xylene by methylation of toluene with, for instance, methanol, methyl chloride or dimethyl ether; PA0 (4) preparation of p-xylene by disproportionation of toluene. PA0 (1) A process for the preparation of liquid hydrocarbons from coal, in which: PA0 (2) A process for the preparation of an aromatic hydrocarbon mixture, in which a mixture of aliphatic oxygen-containing hydrocarbons with the overall formula C.sub.n H.sub.m O.sub.p, which mixture consists for a predominant molar part of one or more compounds for which ##EQU1## is greater than 1, and for the rest of one or more compounds for which ##EQU2## is at most 1, is contacted at elevated temperature with a catalyst according to the invention. PA0 (3) A process for the preparation of an aromatic hydrocarbon mixture from natural gas, in which PA0 (4) A process for the preparation of an aromatic hydrocarbon mixture from methanol, which process is carried out in two steps, dimethyl ether being prepared in the first step by contacting methanol at elevated temperature with a dehydration catalyst, and an aromatic hydrocarbon mixture being prepared in the second step by contacting dimethyl ether originating from the first step at elevated temperature with a catalyst according to the invention. PA0 (5) A process for upgrading a product obtained in the hydrocarbon synthesis according to Fischer-Tropsch, in which from the product a light fraction is separated consisting substantially of components boiling in and/or below the gasoline range and/or a heavy fraction consisting substantially of components boiling above the gasoline range, and in which an aromatic motor gasoline is prepared from the light fraction and/or a fuel with a low pour point from the heavy fraction by contacting the fraction concerned at elevated temperature with a catalyst according to the invention. PA0 (6) A process for the preparation of a hydrocarbon mixture rich in aromatics from a hydrocarbon mixture poor in aromatics boiling in the gasoline range, in which the hydrocarbon mixture poor in aromatics is catalytically reformed and in which at least part of the reformate is contacted at elevated temperature with a catalyst according to the invention. PA0 (7) A process for the preparation of gasoline, in which a hydrocarbon mixture boiling above the gasoline range is cracked using a catalyst mixture containing components A and B, in which a fraction boiling in the gasoline range is separated from the cracked product, in which catalyst component A is a crystalline aluminum silicate zeolite with a pore diameter of more than 9 A, and in which catalyst component B is silicalite. PA0 (8) A process for the preparation of a hydrocarbon mixture boiling in the gasoline range and ethylene, in which PA0 (9) A process for the preparation of a hydrocarbon mixture boiling in the gasoline range, in which PA0 (10) A process for the preparation of a gaseous fuel with a colorific value of at least 30 MJ/m.sup.3, in which PA0 (11) A process for the preparation of an aromatic hydrocarbon mixture, in which a mixture of carbon monoxide and hydrogen with an H.sub.2 /CO molar ratio between 0.25 and 0.75 is contacted with a mixture of two catalysts of which one has the capability of catalyzing the conversion of an H.sub.2 /CO mixture into acyclic oxygen-containing hydrocarbons and the other is a catalyst according to the invention, and in which to the H.sub.2 /CO mixture an amount of water is added which, in %m based on the H.sub.2 /CO mixture, is at least 2.5 and at most ##EQU3## wherein R=the H.sub.2 /CO molar ratio of the feed, and V=the consumption ratio of the H.sub.2 /CO mixture obtained under the conditions at which the above-mentioned process is carried out, but without water addition. PA0 (12) A process for the preparation of a hydrocarbon mixture, in which a mixture of carbon monoxide and hydrogen with an H.sub.2 /CO molar ratio of less than 1.0 is contacted in a first step with a trifunctional catalyst combination containing one or more metal components with catalytic activity for the conversion of an H.sub.2 /CO mixture into acyclic hydrocarbons and/or acyclic oxygen-containing hydrocarbons, one or more metal components with catalytic activity for the water gas shift reaction, and silicalite, and in which at least the C.sub.2.sup.- fraction of the reaction product from the first step is contacted in a second step with a catalyst containing one or more metal components with catalytic activity for the conversion of an H.sub.2 /CO mixture into acyclic hydrocarbons, which metal components have been chosen from the group formed by cobalt, nickel and ruthenium, on the understanding that, if the feed for the second step has an H.sub.2 /CO molar ratio of less than 1.5, water is added to this feed and in the second step a bifunctional catalyst combination is used which contains, in addition to the metal components with catalytic activity for the conversion of an H.sub.2 /CO mixture into acyclic hydrocarbons, also one or more metal components with catalytic activity for the water gas shift reaction.
TABLE A ______________________________________ Radiation: Cu--K Relative intensity d(A) (VS = very strong; S = strong) ______________________________________ 11.1 .+-. 0.2 VS 10.0 .+-. 0.2 VS 3.25 .+-. 0.07 VS 3.22 .+-. 0.07 S 3.76 .+-. 0.05 S 3.72 .+-. 0.05 S ______________________________________
The preparation of silicalite may be carried out by heating an aqueous mixture containing a silicon compound, alkylammonium or phosphonium ions (R.sub.4 X.sup.+) and optionally alkali metal ions (Me.sup.+) and having a pH between 10 and 14, until the crystalline silicalite precursor has formed, and subsequently separating the latter from the mother liquor, and washing, drying and calcining it. The alkylammonium or phosphonium ions may be introduced into the reaction mixture by incorporating into it tetraalkylammonium or phosphonium hydroxides or the salts derived from these compounds, or by forming the quaternary ions in situ, for instance by reaction of a tertiary alkylamine and an alkylhalogenide. Suitable silicon compounds are amorphous silicas and alkali metal silicates. In the preparation of the silicalite the various reaction components should be present in the following ratios, expressed in moles of the oxides per mole quaternary alkylammonium or phosphonium oxide (R.sub.4 X).sub.2 O:
The preparation of the silicalite may very conveniently be carried out by heating the reaction mixture for 5 to 150 hours under autogenous pressure at a temperature between 100.degree. and 250.degree. C.
The uniform pore structure imparts form-selective molecular sieve properties to the silicalite. Thanks to the pore structure, silicalite can be used for separating p-xylene from mixtures with other C.sub.8 aromatics. Silicalite can also be used for separating compounds containing quaternary carbon atoms from mixtures with other organic compounds. Silicalite has a very useful hydrophobic/organophilic characteristic which permits its use in selectively absorbing organic compounds from water.
The applicants have carried out an investigation concerning the use of silicalite for catalytic purposes. This investigation has shown that materials consisting at least partly of silicalite may be advantageously used as catalyst for carrying out a variety of catalytic conversions for the production, i.e., synthesis and/or conversion of hydrocarbon products.